Certain hydraulic systems, such as found in mobile fluid power applications, include a tank or reservoir which receives and stores excess hydraulic fluid. Most of these systems require the hydraulic fluid to be filtered at some point before the fluid reaches the critical components, such as the power cylinders. Typically a filter is installed on a filter head plumbed into the hydraulic tubing or hose, and mounted in the engine compartment or other appropriate structural location. The filter can be located in a filter housing, which itself is removably attached to the filter head; or can be provided as a spin-on unit for easy access and removal.
One known issue with these types of hydraulic systems is that pressures and vacuums are created within the tank during use. In fork lift truck applications, for example, this occurs when the fork as are being raised and lowered and fluid rushes into and is drained from the tank, or when the fork lift truck is operated on uneven surfaces. Breather vents are typically provided in the tank to ensure the proper pressures are maintained for efficient and safe operation of the hydraulic system.
As can be appreciated, such vents are subject to degradation and wear over time. A blocked or inoperable vent can prevent the proper escape or introduction of gasses and air into a tank during operation. In addition, vented gasses can include oil vapor—which raises environmental and cleanliness issues if allowed to escape freely. Likewise, ambient air entering the tank through a vent can include particles which can mix with and contaminate the hydraulic fluid. One solution is to include a filter for the vent. This solves the environmental issues, but increases the repair and maintenance effort required for the hydraulic system, and requires additional stock keeping units apart from the hydraulic fluid filters. Another issue pervasive with hydraulic systems is the amount of space available to mount components (such as filters and vents) on the vehicle chassis or the system frame. As equipment and systems become more compact, the available space for such components comes at a premium and it is a constant struggle to consolidate or arrange components in an efficient manner.
Thus, it is believed that the solutions in the past have not fully and satisfactorily addressed the problems associated with prior hydraulic systems, and particularly with hydraulic systems such as used in mobile fluid power applications. It is therefore believed there is a demand for a hydraulic system which prevents the escape of unfiltered vent gasses from a storage tank; has fewer separate filter components to reduce the stock-keeping units; has a filter that reduces the installation, repair and maintenance costs and efforts necessary for maintaining the system in safe and reliable operation; and efficiently utilizes the available space.